Optical discs are commonly used as storage media for audio-visual (AV) data. These discs are divided into logical units, usually sectors, where data portions are stored. Further, various file systems are available for the organization of the data storage on discs. These file systems can be classified in two types: while in one file system type any data byte position is randomly accessible, the other type of file systems can only access specified data units, e.g. sectors. The latter is the case e.g. for the Universal Disk Format (UDF) specified by the Optical Storage Technology Association (OSTA) at the OSTA website associated with osta.org. File systems generally define e.g. which data units belong to a file. E.g. UDF uses so-called “file entries” for this purpose.
When video data are recorded on an optical disc, e.g. a Digital Versatile Disc (DVD) or Rewritable Blu-ray disc (BD-RE), a hierarchical logical structure is used for the organization of the data. This structure comprises a playlist stored in a playlist file, containing references to clip information files that in turn describe video sequences, also known as clips. The clips contain the actual AV data files. When AV data shall be edited that are recorded on a rewritable optical medium, the editing process usually includes splitting of files. But when a video recording shall be split, the splitting position may be within the smallest accessible data unit, e.g. a sector. In this case, splitting is difficult with a file system that can only access full sectors.
Editing of video data stored on a BD-RE is described e.g. in FIG. 3.1.5.4 of part 3 of the BD-RE description that is available from the official Blu-ray website associated with blu-ravdisc-official. org. It uses the dividing and combining of playlists and newly generated virtual playlists. But it assumes that dividing and combining can be performed at any position within a clip. This is not possible when e.g. UDF is used as file system on the disc.